Articles » Watering Cacti and Succulents

By: John Begeman

Watering Cacti & Succulents

Knowing if, when, and how much to water cacti and

other succulents can be one of the most difficult aspects of growing them successfully. Simply put, they are not like other plants when it comes to their water needs.

Cacti, agaves, aloes, sedums and other succulents have special abilities when it comes to storing and utilizing water. To one degree or another, they all have thick, fleshy, water-storing leaves and, or stems. They also have exceptional methods to limit their water consumption. Surfaces exposed to the drying effects of sun and wind are small in proportion to their total mass. This is especially evident in plants like saguaro and barrel cacti. Thick waxy cuticle layers on outer surfaces help seal in moisture. And a smaller than normal number of pore openings in leaves and stems further restrict moisture loss.

Most native cacti and succulents, when established, can get by just fine on what mother nature supplies here in Tucson. More often than not these plants receive too much water when located in an irrigated landscape. Even if a drip emitter is not located by them, roots of cacti and succulents can travel great distances and obtain water from irrigated parts of the landscape. In some cases they obtain too much water. Saguaros will show signs of over watering which include swelling and cracking of the outer surface. These cracks may extend well into the cactus. Typically, other types of cacti and succulents will simply rot and fall over. Prior to the ocurrence of rot, the plant may begin yellowing. If this occurs, immediately discontinue watering or find the indirect source of water and eliminate it.

When cactus are not getting enough water, their outer skin begins to wrinkle. This is caused by the shrinkage of water-storing tissues in the plant. In the case of segmented cacti, like prickly pear and cholla, the outer pads or segments may also begin falling off. Lack of sufficient moisture in leafy succulents will result in wilting. As water levels in plants such as agave and aloe drop, so does the internal water pressure holding the leaves straight. As a result, leaves begin to bend downward.

Cacti and succulents showing signs of moisture stress can be revived by providing them with a good soaking of water. Keep in mind that the roots of these plants are shallow and widespread, extending out a distance several times their height. Therefore, watering a large area out from the plant, but only a foot or so deep is best. A soaker hose works well for this purpose.

Watering cacti and succulents when they show signs of stress is the way to ensure their survival. However, if you want your cacti and other succulents to thrive, some regular watering will be necessary.

As a general rule, established native cacti and other succulents will benefit from twice-monthly waterings when temperatures are consistently above 90 degrees. May and June are the months when such waterings are most critical.

Newly planted native species will establish quicker when watered on a weekly basis during hot weather. Non-native types of cacti and other succulents, even those well established, will preform better when provided water on a weekly basis. Watering is also a way to promote more rapid growth. Keep in mind that sandy, well-drained soils can tolerate more frequent irrigation than heavy, poorly drained soils. When monsoon rains arrive in July, reduce or discontinue irrigation until the end of the monsoon season in September.

Cacti and other succulents grown in pots are more likely to need regular irrigation than those planted in the ground. During hot, dry weather watering will be needed on a weekly or twice-weekly basis. The soil should be allowed to dry between waterings, even in well drained soil mixes.

Finally, when in doubt about watering, be conservative. More errors are made on the side of over-watering than under-watering. Remember that injury from lack of water develops gradually, and is easy to correct. On the other hand, damage from over watering occurs rapidly and is usually irreversible.

Congratulations to Mrs. Margaret Catlett, the winner of the raffle prize at our recent Master Gardener home garden tour. Margaret won a beautiful pot of mixed annuals, courtesy of the Pima County Master Gardeners.

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Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161.
Material originally appeared in Arizona Daily Star gardening column, on April 30, 2000
- Updated: April 30, 2000

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